Electronic ophthalmic lens with multi-input voting scheme

ABSTRACT

An electronic or powered ophthalmic lens includes one or more systems having one or more batteries or other power sources, power management circuitry, one or more sensors, clock generation circuitry, control algorithms and circuitry, and lens driver circuitry. These systems may change the state of the powered ophthalmic lens. In systems having one or more sensors, a decision making process is required to substantially reduce the possibility of changing the state of the powered ophthalmic lens based upon inaccurate, incomplete or erroneous information supplied by the sensors, changing physiologic conditions , as well as noise and/or interference from internal and external sources.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a powered or electronic ophthalmic lenshaving more than one sensor and associated hardware and software fordetecting purposeful changes in eye states, and more particularly, tomultiple sensors and associated hardware and software configured toimplement voting schemes for detecting changes in desired focal length.

2. Discussion of the Related Art

As electronic devices continue to be miniaturized, it is becomingincreasingly more likely to create wearable or embeddablemicroelectronic devices for a variety of uses. Such uses may includemonitoring aspects of body chemistry, administering controlled dosagesof medications or therapeutic agents via various mechanisms, includingautomatically, in response to measurements, or in response to externalcontrol signals, and augmenting the performance of organs or tissues.Examples of such devices include glucose infusion pumps, pacemakers,defibrillators, ventricular assist devices and neurostimulators. A new,particularly useful field of application is in ophthalmic wearablelenses and contact lenses. For example, a wearable lens may incorporatea lens assembly having an electronically adjustable focus to augment orenhance performance of the eye. In another example, either with orwithout adjustable focus, a wearable contact lens may incorporateelectronic sensors to detect concentrations of particular chemicals inthe precorneal (tear) film. The use of embedded electronics in a lensassembly introduces a potential requirement for communication with theelectronics, for a method of powering and/or re-energizing theelectronics, for interconnecting the electronics, for internal andexternal sensing and/or monitoring, and for control of the electronicsand the overall function of the lens.

The human eye has the ability to discern millions of colors, adjusteasily to shifting light conditions, and transmit signals or informationto the brain at a rate exceeding that of a high-speed internetconnection. Lenses, such as contact lenses and intraocular lenses,currently are utilized to correct vision defects such as myopia(nearsightedness), hyperopia (farsightedness), presbyopia andastigmatism. However, properly designed lenses incorporating additionalcomponents may be utilized to enhance vision as well as to correctvision defects.

Contact lenses may be utilized to correct myopia, hyperopia, astigmatismas well as other visual acuity defects. Contact lenses may also beutilized to enhance the natural appearance of the wearer's eyes. Contactlenses or “contacts” are simply lenses placed on the anterior surface ofthe eye. Contact lenses are considered medical devices and may be wornto correct vision and/or for cosmetic or other therapeutic reasons.Contact lenses have been utilized commercially to improve vision sincethe 1950s. Early contact lenses were made or fabricated from hardmaterials, were relatively expensive and fragile. In addition, theseearly contact lenses were fabricated from materials that did not allowsufficient oxygen transmission through the contact lens to theconjunctiva and cornea which potentially could cause a number of adverseclinical effects. Although these contact lenses are still utilized, theyare not suitable for all patients due to their poor initial comfort.Later developments in the field gave rise to soft contact lenses, basedupon hydrogels, which are extremely popular and widely utilized today.Specifically, silicone hydrogel contact lenses that are available todaycombine the benefit of silicone, which has extremely high oxygenpermeability, with the proven comfort and clinical performance ofhydrogels. Essentially, these silicone hydrogel based contact lenseshave higher oxygen permeability and are generally more comfortable towear than the contact lenses made of the earlier hard materials.

Conventional contact lenses are polymeric structures with specificshapes to correct various vision problems as briefly set forth above. Toachieve enhanced functionality, various circuits and components have tobe integrated into these polymeric structures. For example, controlcircuits, microprocessors, communication devices, power supplies,sensors, actuators, light-emitting diodes, and miniature antennas may beintegrated into contact lenses via custom-built optoelectroniccomponents to not only correct vision, but to enhance vision as well asprovide additional functionality as is explained herein. Electronicand/or powered contract lenses may be designed to provide enhancedvision via zoom-in and zoom-out capabilities, or just simply modifyingthe refractive capabilities of the lenses. Electronic and/or poweredcontact lenses may be designed to enhance color and resolution, todisplay textural information, to translate speech into captions in realtime, to offer visual cues from a navigation system, and to provideimage processing and internet access. The lenses may be designed toallow the wearer to see in low-light conditions. The properly designedelectronics and/or arrangement of electronics on lenses may allow forprojecting an image onto the retina, for example, without avariable-focus optic lens, provide novelty image displays and evenprovide wakeup alerts. Alternately, or in addition to any of thesefunctions or similar functions, the contact lenses may incorporatecomponents for the noninvasive monitoring of the wearer's biomarkers andhealth indicators. For example, sensors built into the lenses may allowa diabetic patient to keep tabs on blood sugar levels by analyzingcomponents of the tear film without the need for drawing blood. Inaddition, an appropriately configured lens may incorporate sensors formonitoring cholesterol, sodium, and potassium levels, as well as otherbiological markers. This, coupled with a wireless data transmitter,could allow a physician to have almost immediate access to a patient'sblood chemistry without the need for the patient to waste time gettingto a laboratory and having blood drawn. In addition, sensors built intothe lenses may be utilized to detect light incident on the eye tocompensate for ambient light conditions or for use in determining blinkpatterns.

The proper combination of devices could yield potentially unlimitedfunctionality; however, there are a number of difficulties associatedwith the incorporation of extra components on a piece of optical-gradepolymer. In general, it is difficult to manufacture such componentsdirectly on the lens for a number of reasons, as well as mounting andinterconnecting planar devices on a non-planar surface. It is alsodifficult to manufacture to scale. The components to be placed on or inthe lens need to be miniaturized and integrated onto just 1.5 squarecentimeters of a transparent polymer while protecting the componentsfrom the liquid environment on the eye. It is also difficult to make acontact lens comfortable and safe for the wearer with the addedthickness of additional components.

Given the area and volume constraints of an ophthalmic device such as acontact lens, and the environment in which it is to be utilized, thephysical realization of the device must overcome a number of problems,including mounting and interconnecting a number of electronic componentson a non-planar surface, the bulk of which comprises optic plastic.Accordingly, there exists a need for providing a mechanically andelectrically robust electronic contact lens.

As these are powered lenses, energy or more particularly currentconsumption, to run the electronics is a concern given batterytechnology on the scale for an ophthalmic lens. In addition to normalcurrent consumption, powered devices or systems of this nature generallyrequire standby current reserves, precise voltage control and switchingcapabilities to ensure operation over a potentially wide range ofoperating parameters, and burst consumption, for example, up to eighteen(18) hours on a single charge, after potentially remaining idle foryears. Accordingly, there exists a need for a system that is optimizedfor low-cost, long-term reliable service, safety and size whileproviding the required power.

In addition, because of the complexity of the functionality associatedwith a powered lens and the high level of interaction between all of thecomponents comprising a powered lens, there is a need to coordinate andcontrol the overall operation of the electronics and optics comprising apowered ophthalmic lens. Accordingly, there is a need for a system tocontrol the operation of all of the other components that is safe,low-cost, and reliable, has a low rate of power consumption and isscalable for incorporation into an ophthalmic lens.

Powered or electronic ophthalmic lenses may have to account for certainunique physiological functions from the individual utilizing the poweredor electronic ophthalmic lens. More specifically, powered lenses mayhave to account for blinking, including the number of blinks in a giventime period, the duration of a blink, the time between blinks and anynumber of possible blink patterns, for example, if the individual isdosing off. Blink detection may also be utilized to provide certainfunctionality, for example, blinking may be utilized as a means tocontrol one or more aspects of a powered ophthalmic lens. Additionally,external factors, such as changes in light intensity levels, and theamount of visible light that a person's eyelid blocks out, have to beaccounted for when determining blinks. For example, if a room has anillumination level between fifty-four (54) and one hundred sixty-one(161) lux, a photosensor should be sensitive enough to detect lightintensity changes that occur when a person blinks.

Ambient light sensors or photosensors are utilized in many systems andproducts, for example, on televisions to adjust brightness according tothe room light, on lights to switch on at dusk, and on phones to adjustthe screen brightness. However, these currently utilized sensor systemsare not small enough and/or do not have low enough power consumption forincorporation into contact lenses.

It is also important to note that different types of blink detectors maybe implemented with computer vision systems directed at one's eye(s),for example, a camera digitized to a computer. Software running on thecomputer can recognize visual patterns such as the eye open and closed.These systems may be utilized in ophthalmic clinical settings fordiagnostic purposes and studies. Unlike the above described detectorsand systems, these systems are intended for off eye use and to look atrather than look away from the eye. Although these systems are not smallenough to be incorporated into contact lenses, the software utilized maybe similar to the software that would work in conjunction with poweredcontact lenses. Either system may incorporate software implementationsof artificial neural networks that learn from input and adjust theiroutput accordingly. Alternately, non-biology based softwareimplementations incorporating statistics, other adaptive algorithms,and/or signal processing may be utilized to create smart systems.

Accordingly, there exists a need for a means and method for detectingcertain physiological functions, such as a blink, and utilizing them toactivate and/or control an electronic or powered ophthalmic lensaccording to the type of blink sequence detected by a sensor. The sensorbeing utilized having to be sized and configured for use in a contactlens. Other sensors and sensor systems may be utilized as well. Forexample, a pupil position and convergence detection system may beutilized to change the state of a powered ophthalmic lens.

Systems which comprise multiple sensors may require an added degree ofcomplexity but may also include added functionality, convenience, andother parameters important to users. Rather than relying on a singleinput to determine an output, multi-sensor systems may improvereliability, functionality, safety, and convenience, for example, byreducing false positive and false negative determinations. Systems whichconsider multiple sensor inputs before determining the need for statechange are common in the art, for example, a safe which requires both aphysical key and a numeric code before unlocking. Systems have also beenproposed for changing the state of electronic or powered ophthalmicdevices, for example, using purposeful blink patterns to change thestate of a variable-focus lens between near and distance focal length.It should be appreciated that safety and reliability are of utmostimportance with a powered ophthalmic device, but convenience andfunctionality are also important aspects of the system or device.Accordingly, there exists a need for a system in an electronic orpowered ophthalmic lens which considers multiple sensor inputs todetermine a requested or desired change in state while minimizing falsetriggering.

SUMMARY OF THE INVENTION

The electronic ophthalmic lens with a multi-input voting scheme inaccordance with the present invention overcomes the limitationsassociated with the prior art as briefly described above. The presentinvention comprises a voting scheme that considers multiple inputs andmay be integrated into an ophthalmic device with the associatedrequirements for safety, convenience, low power consumption and smallsize.

In accordance with one aspect, the present invention is directed to amethod for controlling functions in a powered ophthalmic lens. Themethod comprises the steps of sampling multiple sensors incorporatedinto the ophthalmic lens, the sensors measuring physiologic,environmental or other changes, determining the results from themultiple sensors, including making comparisons to thresholds andcomparisons to predetermined patterns, aggregating the results from themultiple sensors to generate a single decision signal, and configuringan actuator based on the single decision signal to implement a change infunction of or maintain a function of the powered ophthalmic lens.

In accordance with another aspect, the present invention is directed toa powered ophthalmic lens. The powered ophthalmic lens comprises acontact lens including an optic zone and a peripheral zone, and at leaston electronic system incorporated into the peripheral zone of thecontact lens, the electronic system including multiple sensors, a systemcontroller and at least one actuator, the system controller configuredto implement a process for controlling the functions of the poweredophthalmic lens, the process comprising the steps of sampling themultiple sensors, determining the results from the multiple sensorsincluding making comparisons to thresholds and comparisons topredetermined patterns, aggregating the results from the multiplesensors to generate a single decision signal and configuring theactuator based upon the single decision signal to implement a change infunction of or maintain a function of the powered ophthalmic lens.

In accordance with yet another aspect, the present invention is directedto a powered ophthalmic lens. The powered ophthalmic lens comprises acontact lens, and at least on electronic system incorporated into thecontact lens, the electronic system including multiple sensors, a systemcontroller and at least one actuator, the system controller configuredto implement a process for controlling the functions of the poweredophthalmic lens, the process comprising the steps of sampling themultiple sensors, determining the results from the multiple sensorsincluding making comparisons to thresholds and comparisons topredetermined patterns, aggregating the results from the multiplesensors to generate a single decision signal and configuring theactuator based upon the single decision signal to implement a change infunction of or maintain a function of the powered ophthalmic lens.

In accordance with yet still another aspect, the present invention isdirected to a powered ophthalmic lens. The powered ophthalmic lenscomprises an intraocular contact lens, and at least on electronic systemincorporated into the intraocular lens, the electronic system includingmultiple sensors, a system controller and at least one actuator, thesystem controller configured to implement a process for controlling thefunctions of the powered ophthalmic lens, the process comprising thesteps of sampling the multiple sensors, determining the results from themultiple sensors including making comparisons to thresholds andcomparisons to predetermined patterns, aggregating the results from themultiple sensors to generate a single decision signal and configuringthe actuator based upon the single decision signal to implement a changein function of or maintain a function of the powered ophthalmic lens.

The present invention relates more generally to a powered contact lenscomprising an electronic system, which performs any number of functions,including actuating a variable-focus optic if included. The electronicsystem includes one or more batteries or other power sources, powermanagement circuitry, one or more sensors, clock generation circuitry,control algorithms and circuitry, and lens driver circuitry.

Control of a powered ophthalmic lens may be accomplished through amanually operated external device that communicates with the lenswirelessly, such as a hand-held remote unit. Alternately, control of thepowered ophthalmic lens may be accomplished via feedback or controlsignals directly from the wearer. For example, sensors built into thelens may detect blinks and/or blink patterns. Based upon the pattern orsequence of blinks, the powered ophthalmic lens may change state, forexample, its refractive power in order to either focus on a near objector a distant object.

The blink detection algorithm is a component of the system controllerwhich detects characteristics of blinks, for example, if the lid is openor closed, the duration of the blink open or closed, the inter-blinkduration, and the number of blinks in a given time period. The exemplaryalgorithm in accordance with the present invention relies on samplinglight incident on the eye at a certain sample rate. Pre-determined blinkpatterns are stored and compared to the recent history of incident lightsamples. When patterns match, the blink detection algorithm triggersactivity in the system controller, for example, to activate the lensdriver to change the refractive power of the lens.

The blink detection algorithm and associated circuitry of the presentinvention preferably operate over a reasonably wide range of lightingconditions and is preferably able to distinguish an intentional blinksequence from involuntary blinks. It is also preferred that minimaltraining is required to utilize intentional blinks to activate and/orcontrol the powered ophthalmic lens. The blink detection algorithm andassociated circuitry of the present invention provides a safe, low cost,and reliable means and method for detecting blinks via a powered orelectronic contact lens, which also has a low rate of power consumptionand is scalable for incorporation into an ophthalmic lens, for at leastone of activating or controlling a powered or electronic ophthalmiclens.

Existing multi-input systems, herein referred to as voting schemes, arenot specifically engineered to consider the necessary inputs for anelectronic ophthalmic lens, nor the necessary outputs. For example,voting schemes for an electronic ophthalmic lens may need to consider anumber of factors, including eye impedance, pupil convergence, and pupildilation instead of those sensor inputs common in other voting schemes.

In an electronic ophthalmic lens, the desire to change states, forexample, between near distance and far distance focus, should bedetermined with preferably no false positives or false negatives. Afalse positive could, for example, result in an electronic or poweredlens having a variable power optic lens changing state to near distancefocus when the user is driving on the highway and needs distance vision.Likewise, a false negative detection could result in the variable poweroptic lens staying at a far focal length when the user wants to read upclose. It should be appreciated that a false trigger is not limitedexclusively to changes in focal length and may affect other changes ofstate such as detecting a drowsy user or selecting an item on a heads-updisplay akin to a “single click” with a mouse in a graphical userinterface.

Proposed sensor systems for electronic ophthalmic lenses consider singleinputs, for example, the change in impedance across the eye whichcorrelates to ciliary muscle activity and hence the desire for a changein focal length. Each of these sensors may be subject to limitationssuch as noise, dynamic range, and interference, which in turn increasethe possibility of false triggering. For example, a system whichconsiders pupil diameter may record dilation caused by a decrease inambient light rather than a change in the desired focal length.

Accordingly, there exists the need for a system in an electronicophthalmic device which considers multiple sensor inputs to determine arequested change in state while minimizing false triggering. Theinvention described herein considers multiple inputs and may beintegrated into an ophthalmic device, with the associated requirementsfor safety, convenience, low power, and small size.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIG. 1 illustrates an exemplary contact lens comprising a blinkdetection system in accordance with some embodiments of the presentinvention.

FIG. 2 illustrates a graphical representation of light incident on thesurface of the eye versus time, illustrating a possible involuntaryblink pattern recorded at various light intensity levels versus time anda usable threshold level based on some point between the maximum andminimum light intensity levels in accordance with the present invention.

FIG. 3 is an exemplary state transition diagram of a blink detectionsystem in accordance with the present invention.

FIG. 4 is a diagrammatic representation of a photodetection pathutilized to detect and sample received light signals in accordance withthe present invention.

FIG. 5 is a block diagram of digital conditioning logic in accordancewith the present invention.

FIG. 6 is a block diagram of digital detection logic in accordance withthe present invention.

FIG. 7 is an exemplary timing diagram in accordance with the presentinvention.

FIG. 8 is a diagrammatic representation of a digital system controllerin accordance with the present invention.

FIGS. 9A through 9G are exemplary timing diagrams for automatic gaincontrol in accordance with the present invention.

FIG. 10 is a diagrammatic representation of light-blocking andlight-passing regions on an exemplary integrated circuit die inaccordance with the present invention.

FIG. 11 is a diagrammatic representation of an exemplary electronicinsert, including a blink detector, for a powered contact lens inaccordance with the present invention.

FIG. 12 is a block diagram of a generic system having multiple sensors,a system controller and an actuator, wherein an activation decision ismade based on the output of two or more sensors in accordance with thepresent invention.

FIG. 13 is a flow chart of an exemplary process by which a systemcontroller determines if the state of an actuator is to be changed basedupon sensor inputs in accordance with the present invention.

FIG. 14 graphically illustrates various exemplary sensor inputs in anelectronic ophthalmic lens designed to determine the need to change thefocal state of the ophthalmic lens versus time in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Conventional contact lenses are polymeric structures with specificshapes to correct various vision problems as briefly set forth above. Toachieve enhanced functionality, various circuits and components may beintegrated into these polymeric structures. For example, controlcircuits, microprocessors, communication devices, power supplies,sensors, actuators, light-emitting diodes, and miniature antennas may beintegrated into contact lenses via custom-built optoelectroniccomponents to not only correct vision, but to enhance vision as well asprovide additional functionality as is explained herein. Electronicand/or powered contact lenses may be designed to provide enhanced visionvia zoom-in and zoom-out capabilities, or just simply modifying therefractive capabilities of the lenses. Electronic and/or powered contactlenses may be designed to enhance color and resolution, to displaytextural information, to translate speech into captions in real time, tooffer visual cues from a navigation system, and to provide imageprocessing and internet access. The lenses may be designed to allow thewearer to see in low light conditions. The properly designed electronicsand/or arrangement of electronics on lenses may allow for projecting animage onto the retina, for example, without a variable focus optic lens,provide novelty image displays and even provide wakeup alerts.Alternately, or in addition to any of these functions or similarfunctions, the contact lenses may incorporate components for thenoninvasive monitoring of the wearer's biomarkers and health indicators.For example, sensors built into the lenses may allow a diabetic patientto keep tabs on blood sugar levels by analyzing components of the tearfilm without the need for drawing blood. In addition, an appropriatelyconfigured lens may incorporate sensors for monitoring cholesterol,sodium, and potassium levels, as well as other biological markers. Thiscoupled with a wireless data transmitter could allow a physician to havealmost immediate access to a patient's blood chemistry without the needfor the patient to waste time getting to a laboratory and having blooddrawn. In addition, sensors built into the lenses may be utilized todetect light incident on the eye to compensate for ambient lightconditions or for use in determining blink patterns.

The powered or electronic contact lens of the present inventioncomprises the necessary elements to correct and/or enhance the vision ofpatients with one or more of the above described vision defects orotherwise perform a useful ophthalmic function. In addition, theelectronic contact lens may be utilized simply to enhance normal visionor provide a wide variety of functionality as described above. Theelectronic contact lens may comprise a variable focus optic lens, anassembled front optic embedded into a contact lens or just simplyembedding electronics without a lens for any suitable functionality. Theelectronic lens of the present invention may be incorporated into anynumber of contact lenses as described above. In addition, intraocularlenses may also incorporate the various components and functionalitydescribed herein. However, for ease of explanation, the disclosure willfocus on an electronic contact lens to correct vision defects intendedfor single-use daily disposability.

The present invention may be employed in a powered ophthalmic lens orpowered contact lens comprising an electronic system, which actuates avariable-focus optic or any other device or devices configured toimplement any number of numerous functions that may be performed. Theelectronic system includes one or more batteries or other power sources,power management circuitry, one or more sensors, clock generationcircuitry, control algorithms and circuitry, and lens driver circuitry.The complexity of these components may vary depending on the required ordesired functionality of the lens.

Control of an electronic or a powered ophthalmic lens may beaccomplished through a manually operated external device thatcommunicates with the lens, such as a hand-held remote unit. Forexample, a fob may wirelessly communicate with the powered lens basedupon manual input from the wearer. Alternately, control of the poweredophthalmic lens may be accomplished via feedback or control signalsdirectly from the wearer. For example, sensors built into the lens maydetect blinks and/or blink patterns. Based upon the pattern or sequenceof blinks, the powered ophthalmic lens may change state, for example,its refractive power in order to either focus on a near object or adistant object.

Alternately, blink detection in a powered or electronic ophthalmic lensmay be used for other various uses where there is interaction betweenthe user and the electronic contact lens, such as activating anotherelectronic device, or sending a command to another electronic device.For example, blink detection in an ophthalmic lens may be used inconjunction with a camera on a computer wherein the camera keeps trackof where the eye(s) moves on the computer screen, and when the userexecutes a blink sequence that it detected, it causes the mouse pointerto perform a command, such as double-clicking on an item, highlightingan item, or selecting a menu item.

A blink detection algorithm is a component of the system controllerwhich detects characteristics of blinks, for example, is the lid open orclosed, the duration of the blink, the inter-blink duration, and thenumber of blinks in a given time period. The algorithm in accordancewith the present invention relies on sampling light incident on the eyeat a certain sample rate. Pre-determined blink patterns are stored andcompared to the recent history of incident light samples. When patternsmatch, the blink detection algorithm may trigger activity in the systemcontroller, for example, to activate the lens driver to change therefractive power of the lens.

Blinking is the rapid closing and opening of the eyelids and is anessential function of the eye. Blinking protects the eye from foreignobjects, for example, individuals blink when objects unexpectedly appearin proximity to the eye. Blinking provides lubrication over the anteriorsurface of the eye by spreading tears. Blinking also serves to removecontaminants and/or irritants from the eye. Normally, blinking is doneautomatically, but external stimuli may contribute as in the case withirritants. However, blinking may also be purposeful, for example, forindividuals who are unable to communicate verbally or with gestures canblink once for yes and twice for no. The blink detection algorithm andsystem of the present invention utilizes blinking patterns that cannotbe confused with normal blinking response. In other words, if blinkingis to be utilized as a means for controlling an action, then theparticular pattern selected for a given action cannot occur at random;otherwise inadvertent actions may occur. As blink speed may be affectedby a number of factors, including fatigue, eye injury, medication anddisease, blinking patterns for control purposes preferably account forthese and any other variables that affect blinking. The average lengthof involuntary blinks is in the range of about one hundred (100) to fourhundred (400) milliseconds. Average adult men and women blink at a rateof ten (10) involuntary blinks per minute, and the average time betweeninvoluntary blinks is about 0.3 to seventy (70) seconds.

An exemplary embodiment of the blink detection algorithm may besummarized in the following steps.

1. Define an intentional “blink sequence” that a user will execute forpositive blink detection.

2. Sample the incoming light level at a rate consistent with detectingthe blink sequence and rejecting involuntary blinks.

3. Compare the history of sampled light levels to the expected “blinksequence,” as defined by a blink template of values.

4. Optionally implement a blink “mask” sequence to indicate portions ofthe template to be ignored during comparisons, e.g. near transitions.This may allow for a user to deviate from a desired “blink sequence,”such as a plus or minus one (1) error window, wherein one or more oflens activation, control, and focus change can occur. Additionally, thismay allow for variation in the user's timing of the blink sequence.

An exemplary blink sequence may be defined as follows:

1. blink (closed) for 0.5 s

2. open for 0.5 s

3. blink (closed) for 0.5 s

At a one hundred (100) ms sample rate, a twenty (20) sample blinktemplate is given by

blink_template=[1,1,1, 0,0,0,0,0, 1,1,1,1,1, 0,0,0,0,0, 1,1].

The blink mask is defined to mask out the samples just after atransition (0 to mask out or ignore samples), and is given by

blink_mask=[1,1,1, 0,1,1,1,1, 0,1,1,1,1, 0,1,1,1,1, 0,1].

Optionally, a wider transition region may be masked out to allow formore timing uncertainty, and is given by

blink_mask=[1,1,0, 0,1,1,1,0, 0,1,1,1,0, 0,1,1,1,0, 0,1].

Alternate patterns may be implemented, e.g. single long blink, in thiscase a 1.5 s blink with a 24-sample template, given by

blink_template=[1,1,1,1,0,0, 0,0,0,0,0,0, 0,0,0,0,0,0, 0,1,1,1,1,1].

It is important to note that the above example is for illustrativepurposes and does not represent a specific set of data.

Detection may be implemented by logically comparing the history ofsamples against the template and mask. The logical operation is toexclusive-OR (XOR) the template and the sample history sequence, on abitwise basis, and then verify that all unmasked history bits match thetemplate. For example, as illustrated in the blink mask samples above,in each place of the sequence of a blink mask that the value is logic 1,a blink has to match the blink mask template in that place of thesequence. However, in each place of the sequence of a blink mask thatthe value is logic 0, it is not necessary that a blink matches the blinkmask template in that place of the sequence. For example, the followingBoolean algorithm equation, as coded in MATLAB®, may be utilized.

matched=not (blink_mask)|not (xor (blink_template, test_sample)),

wherein test_sample is the sample history. The matched value is asequence with the same length as the blink template, sample history andblink_mask. If the matched sequence is all logic 1's, then a good matchhas occurred. Breaking it down, not (xor (blink_template, test_sample))gives a logic 0 for each mismatch and a logic 1 for each match. Logicoring with the inverted mask forces each location in the matchedsequence to a logic 1 where the mask is a logic 0. Accordingly, the moreplaces in a blink mask template where the value is specified as logic 0,the greater the margin of error in relation to a person's blinks isallowed. MATLAB® is a high level language and implementation fornumerical computation, visualization and programming and is a product ofMathWorks, Natick, Mass. It is also important to note that the greaterthe number of logic 0's in the blink mask template, the greater thepotential for false positive matched to expected or intended blinkpatterns. It should be appreciated that a variety of expected orintended blink patterns may be programmed into a device with one or moreactive at a time. More specifically, multiple expected or intended blinkpatterns may be utilized for the same purpose or functionality, or toimplement different or alternate functionality. For example, one blinkpattern may be utilized to cause the lens to zoom in or out on anintended object while another blink pattern may be utilized to causeanother device, for example, a pump, on the lens to deliver a dose of atherapeutic agent.

FIG. 1 illustrates, in block diagram form, a contact lens 100,comprising an electronic blink detector system, in accordance with anexemplary embodiment of the present invention. In this exemplaryembodiment, the electronic blink detector system may comprise aphotosensor 102, an amplifier 104, an analog-to-digital converter or ADC106, a digital signal processor 108, a power source 110, an actuator112, and a system controller 114.

When the contact lens 100 is placed onto the front surface of a user'seye the electronic circuitry of the blink detector system may beutilized to implement the blink detection algorithm of the presentinvention. The photosensor 102, as well as the other circuitry, isconfigured to detect blinks and/or various blink patterns produced bythe user's eye.

In this exemplary embodiment, the photosensor 102 may be embedded intothe contact lens 100 and receives ambient light 101, converting incidentphotons into electrons and thereby causing a current, indicated by arrow103, to flow into the amplifier 104. The photosensor or photodetector102 may comprise any suitable device. In one exemplary embodiment, thephotosensor 102 comprises a photodiode. In a preferred exemplaryembodiment, the photodiode is implemented in a complimentary metal-oxidesemiconductor (CMOS process technology) to increase integration abilityand reduce the overall size of the photosensor 102 and the othercircuitry. The current 103 is proportional to the incident light leveland decreases substantially when the photodetector 102 is covered by aneyelid. The amplifier 104 creates an output proportional to the input,with gain, and may function as a transimpedance amplifier which convertsinput current into output voltage. The amplifier 104 may amplify asignal to a useable level for the remainder of the system, such asgiving the signal enough voltage and power to be acquired by the ADC106. For example, the amplifier may be necessary to drive subsequentblocks since the output of the photosensor 102 may be quite small andmay be used in low-light environments. The amplifier 104 may beimplemented as a variable-gain amplifier, the gain of which may beadjusted by the system controller 114, in a feedback arrangement, tomaximize the dynamic range of the system. In addition to providing gain,the amplifier 104 may include other analog signal conditioningcircuitry, such as filtering and other circuitry appropriate to thephotosensor 102 and amplifier 104 outputs. The amplifier 104 maycomprise any suitable device for amplifying and conditioning the signaloutput by the photosensor 102. For example, the amplifier 104 may simplycomprise a single operational amplifier or a more complicated circuitcomprising one or more operational amplifiers. As set forth above, thephotosensor 102 and the amplifier 104 are configured to detect andisolate blink sequences based upon the incident light intensity receivedthrough the eye and convert the input current into a digital signalusable ultimately by the system controller 114. The system controller114 is preferably preprogrammed or preconfigured to recognize variousblink sequences and/or blink patterns in various light intensity levelconditions and provide an appropriate output signal to the actuator 112.The system controller 114 also comprises associated memory.

In this exemplary embodiment, the ADC 106 may be used to convert acontinuous, analog signal output from the amplifier 104 into a sampled,digital signal appropriate for further signal processing. For example,the ADC 106 may convert an analog signal output from the amplifier 104into a digital signal that may be useable by subsequent or downstreamcircuits, such as a digital signal processing system or microprocessor108. A digital signal processing system or digital signal processor 108may be utilized for digital signal processing, including one or more offiltering, processing, detecting, and otherwise manipulating/processingsampled data to permit incident light detection for downstream use. Thedigital signal processor 108 may be preprogrammed with the blinksequences and/or blink patterns described above. The digital signalprocessor 108 also comprises associated memory. The digital signalprocessor 108 may be implemented utilizing analog circuitry, digitalcircuitry, software, or a combination thereof. In the illustrateexemplary embodiment, it is implemented in digital circuitry. The ADC106 along with the associated amplifier 104 and digital signal processor108 are activated at a suitable rate in agreement with the sampling ratepreviously described, for example every one hundred (100) ms.

A power source 110 supplies power for numerous components comprising theblink detection system. The power may be supplied from a battery, energyharvester, or other suitable means as is known to one of ordinary skillin the art. Essentially, any type of power source 110 may be utilized toprovide reliable power for all other components of the system. A blinksequence may be utilized to change the state of the system and/or thesystem controller. Furthermore, the system controller 114 may controlother aspects of a powered contact lens depending on input from thedigital signal processor 108, for example, changing the focus orrefractive power of an electronically controlled lens through theactuator 112.

The system controller 114 uses the signal from the photosensor chain;namely, the photosensor 102, the amplifier 104, the ADC 106 and thedigital signal processing system 108, to compare sampled light levels toblink activation patterns. Referring to FIG. 2, a graphicalrepresentation of blink pattern samples recorded at various lightintensity levels versus time and a usable threshold level isillustrated. Accordingly, accounting for various factors may mitigateand/or prevent error in detecting blinks when sampling light incident onthe eye, such as accounting for changes in light intensity levels indifferent places and/or while performing various activities.Additionally, when sampling light incident on the eye, accounting forthe effects that changes in ambient light intensity may have on the eyeand eyelid may also mitigate and/or prevent error in detecting blinks,such as how much visible light an eyelid blocks when it is closed inlow-intensity light levels and in high-intensity light levels. In otherwords, in order to prevent erroneous blinking patterns from beingutilized to control, the level of ambient light is preferably accountedfor as is explained in greater detail below.

For example, in a study, it has been found that the eyelid on averageblocks approximately ninety-nine (99) percent of visible light, but atlower wavelengths less light tends to be transmitted through the eyelid,blocking out approximately 99.6 percent of visible light. At longerwavelengths, toward the infrared portion of the spectrum, the eyelid mayblock only thirty (30) percent of the incident light. What is importantto note; however, is that light at different frequencies, wavelengthsand intensities may be transmitted through the eyelids with differentefficiencies. For example, when looking at a bright light source, anindividual may see red light with his or her eyelids closed. There mayalso be variations in how much visible light an eyelid blocks based uponan individual, such as an individual's skin pigmentation. As isillustrated in FIG. 2, data samples of blink patterns across variouslighting levels are simulated over the course of a seventy (70) secondtime interval wherein the visible light intensity levels transmittedthrough the eye are recorded during the course of the simulation, and ausable threshold value is illustrated. The threshold is set at a valuein between the peak-to-peak value of the visible light intensityrecorded for the sample blink patterns over the course of the simulationat varying light intensity levels. Having the ability to preprogramblink patterns while tracking an average light level over time andadjusting a threshold may be critical to being able to detect when anindividual is blinking, as opposed to when an individual is not blinkingand/or there is just a change in light intensity level in a certainarea.

Referring now again to FIG. 1, in further alternate exemplaryembodiments, the system controller 114 may receive input from sourcesincluding one or more of a blink detector, eye muscle sensors, and a fobcontrol. By way of generalization, it may be obvious to one skilled inthe art that the method of activating and/or controlling the systemcontroller 114 may require the use of one or more activation methods.For example, an electronic or powered contact lens may be programmablespecific to an individual user, such as programming a lens to recognizeboth of an individual's blink patterns and an individual's ciliarymuscle signals when performing various actions, for example, focusing onan object far away, or focusing on an object that is near. In someexemplary embodiments, using more than one method to activate anelectronic contact lens, such as blink detection and ciliary musclesignal detection, may give the ability for each method to becrosschecked with another before activation of the contact lens occurs.An advantage of crosschecking may include mitigation of false positives,such as minimizing the chance of unintentionally triggering a lens toactivate. In one exemplary embodiment, the crosschecking may involve avoting scheme, wherein a certain number of conditions are met prior toany action taking place.

The actuator 112 may comprise any suitable device for implementing aspecific action based upon a received command signal. For example, if ablink activation pattern is matched compared to a sampled light level asdescribed above, the system controller 114 may enable the actuator 112,such as a variable-optic electronic or powered lens. The actuator 112may comprise an electrical device, a mechanical device, a magneticdevice, or any combination thereof. The actuator 112 receives a signalfrom the system controller 114 in addition to power from the powersource 110 and produces some action based on the signal from the systemcontroller 114. For example, if the system controller 114 signal isindicative of the wearer trying to focus on a near object, the actuator112 may be utilized to change the refractive power of the electronicophthalmic lens, for example, via a dynamic multi-liquid optic zone. Inan alternate exemplary embodiment, the system controller 114 may outputa signal indicating that a therapeutic agent should be delivered to theeye(s). In this exemplary embodiment, the actuator 112 may comprise apump and reservoir, for example, a microelectromechanical system (MEMS)pump. As set forth above, the powered lens of the present invention mayprovide various functionality; accordingly, one or more actuators may bevariously configured to implement the functionality.

FIG. 3 illustrates a state transition diagram 300 for an exemplary blinkdetection system in accordance with the blink detection algorithm of thepresent invention. The system starts in an IDLE state 302 waiting for anenable signal bl_go to be asserted. When the enable bl_go signal isasserted, for example, by an oscillator and control circuit which pulsesbl_go at a one hundred (100) ms rate commensurate with the blinksampling rate, the state machine then transitions to a WAIT_ADC state304 in which an ADC is enabled to convert a received light level to adigital value. The ADC asserts an adc_done signal to indicate itsoperations are complete, and the system or state machine transitions toa SHIFT state 306. In the SHIFT state 306 the system pushes the mostrecently received ADC output value onto a shift register to hold thehistory of blink samples. In some exemplary embodiments, the ADC outputvalue is first compared to a threshold value to provide a single bit (1or 0) for the sample value, in order to minimize storage requirements.The system or state machine then transitions to a COMPARE state 308 inwhich the values in the sample history shift register are compared toone or more blink sequence templates and masks as described above. If amatch is detected, one or more output signals may be asserted, such asone to toggle the state of the lens driver, bl_cp_toggle, or any otherfunctionality to be performed by the powered ophthalmic lens. The systemor state machine then transitions to the DONE state 310 and asserts abl_done signal to indicate its operations are complete.

FIG. 4 illustrates an exemplary photosensor or photodetector signal pathpd_rx_top that may be used to detect and sample received light levels.The signal path pd_rx_top may comprise a photodiode 402, atransimpedance amplifier 404, an automatic gain and low pass filteringstage 406 (AGC/LPF), and an ADC 408. The adc_vref signal is input to theADC 408 from the power source 110 (see FIG. 1) or alternately it may beprovided from a dedicated circuit inside the analog-to-digital converter408. The output from the ADC 408, adc_data, is transmitted to thedigital signal processing and system controller block 108/114 (see FIG.1). Although illustrated in FIG. 1 as individual blocks 108 and 114, forease of explanation, the digital signal processing and system controllerare preferably implemented on a single block 410. The enable signal,adc_en, the start signal, adc_start, and the reset signal, adc_rst_n arereceived from the digital signal processing and system controller 410while the complete signal, adc_complete, is transmitted thereto. Theclock signal, adc_clk, may be received from a clock source external tothe signal path, pd_rx_top, or from the digital signal processing andsystem controller 410. It is important to note that the adc_clk signaland the system clock may be running at different frequencies. It is alsoimportant to note that any number of different ADCs may be utilized inaccordance with the present invention which may have different interfaceand control signals but which perform a similar function of providing asampled, digital representation of the output of the analog portion ofthe photosensor signal path. The photodetect enable, pd_en, and thephotodetect gain, pd_gain, are received from the digital signalprocessing and system controller 410.

FIG. 5 illustrates a block diagram of digital conditioning logic 500that may be used to reduce the received ADC signal value, adc_data, to asingle bit value pd_data. The digital conditioning logic 500 maycomprise a digital register 502 to receive the data, adc_data, from thephotodetection signal path pd_rx_top to provide a held value on thesignal adc_data_held. The digital register 502 is configured to accept anew value on the adc_data signal when the adc_complete signal isasserted and to otherwise hold the last accepted value when theadc_complete signal is received. In this manner the system may disablethe photodetection signal path once the data is latched to reduce systemcurrent consumption. The held data value may then be averaged, forexample, by an integrate-and-dump average or other averaging methodsimplemented in digital logic, in the threshold generation circuit 504 toproduce one or more thresholds on the signal pd_th. The held data valuemay then be compared, via comparator 506, to the one or more thresholdsto produce a one-bit data value on the signal pd_data. It will beappreciated that the comparison operation may employ hysteresis orcomparison to one or more thresholds to minimize noise on the outputsignal pd_data. The digital conditioning logic may further comprise again adjustment block pd_gain_adj 508 to set the gain of the automaticgain and low-pass filtering stage 406 in the photodetection signal pathvia the signal pd_gain, illustrated in FIG. 4, according to thecalculated threshold values and/or according to the held data value. Itis important to note that in this exemplary embodiment six bit wordsprovide sufficient resolution over the dynamic range for blink detectionwhile minimizing complexity.

In one exemplary embodiment, the threshold generation circuit 504comprises a peak detector, a valley detector and a threshold calculationcircuit. In this exemplary embodiment, the threshold and gain controlvalues may be generated as follows. The peak detector and the valleydetector are configured to receive the held value on signaladc_data_held. The peak detector is further configured to provide anoutput value, pd_pk, which quickly tracks increases in the adc_data_heldvalue and slowly decays if the adc_data_held value decreases. Theoperation is analogous to that of a classic diode envelope detector, asis well-known in the electrical arts. The valley detector is furtherconfigured to provide an output value pd_vl which quickly tracksdecreases in the adc_data_held value and slowly decays to a higher valueif the adc_data_held value increases. The operation of the valleydetector is also analogous to a diode envelope detector, with thedischarge resistor tied to a positive power supply voltage. Thethreshold calculation circuit is configured to receive the pd_pl andpd_vl values and is further configured to calculate a mid-pointthreshold value pd_th_mid based on an average of the pd_pk and pd_vlvalues. The threshold generation circuit 504 provides the thresholdvalue pd_th based on the mid-point threshold value pd_th_mid.

The threshold generation circuit 504 may be further adapted to updatethe values of the pd_pk and pd_vl levels in response to changes in thepd_gain value. If the pd_gain value increases by one step, then thepd_pk and pd_vl values are increased by a factor equal to the expectedgain increase in the photodetection signal path. If the pd_gain valuedecreases by one step, then the pd_pk and pd_val values are decreased bya factor equal to the expected gain decrease in the photodetectionsignal path. In this manner the states of the peak detector and valleydetectors, as held in the pd_pk and pd_vl values, respectively, and thethreshold value pd_th as calculated from the pd_pk and pd_vl values areupdated to match the changes in signal path gain, thereby avoidingdiscontinuities or other changes in state or value resulting only fromthe intentional change in the photodetection signal path gain.

In a further exemplary embodiment of the threshold generation circuit504, the threshold calculation circuit may be further configured tocalculate a threshold value pd_th_pk based on a proportion or percentageof the pd_pk value. In a preferred exemplary embodiment the pd_th_pk maybe advantageously configured to be seven eighths of the pd_pk value, acalculation which may be implemented with a simple right shift by threebits and a subtraction as is well-known in the relevant art. Thethreshold calculation circuit may select the threshold value pd_th to bethe lesser of pd_th_mid and pd_th_pk. In this manner, the pd_th valuewill never be equal to the pd_pk value, even after long periods ofconstant light incident on the photodiode which may result in the pd_pkand pd_vl values being equal. It will be appreciated that the pd_th_pkvalue ensures detection of a blink after long intervals. The behavior ofthe threshold generation circuit is further illustrated in FIG. 9, asdiscussed subsequently.

FIG. 6 illustrates a block diagram of digital detection logic 600 thatmay be used to implement an exemplary digital blink detection algorithmin accordance with an embodiment of the present invention. The digitaldetection logic 600 may comprise a shift register 602 adapted to receivethe data from the photodetection signal path pd_rx_top, FIG. 4, or fromthe digital conditioning logic, FIG. 5, as illustrated here on thesignal pd_data, which has a one bit value. The shift register 602 holdsa history of the received sample values, here in a 24-bit register. Thedigital detection logic 600 further comprises a comparison block 604,adapted to receive the sample history and one or more blink templatesbl_tpl and blink masks bl_mask, and is configured to indicate a match tothe one or more templates and masks on one or more output signals thatmay be held for later use. The output of the comparison block 604 islatched via a D flip-flop 606. The digital detection logic 600 mayfurther comprise a counter 608 or other logic to suppress successivecomparisons that may be on the same sample history set at small shiftsdue to the masking operations. In a preferred exemplary embodiment thesample history is cleared or reset after a positive match is found, thusrequiring a full, new matching blink sequence to be sampled before beingable to identify a subsequent match. The digital detection logic 600 maystill further comprise a state machine or similar control circuitry toprovide the control signals to the photodetection signal path and theADC. In some exemplary embodiments the control signals may be generatedby a control state machine that is separate from the digital detectionlogic 600. This control state machine may be part of the digital signalprocessing and system controller 410.

FIG. 7 illustrates a timing diagram of the control signals provided froma blink detection subsystem to an ADC 408 (FIG. 4) used in aphotodetection signal path. The enable and clock signals adc_en,adc_rst_n and adc_clk are activated at the start of a sample sequenceand continue until the analog-to-digital conversion process is complete.In one exemplary embodiment the ADC conversion process is started when apulse is provided on the adc_start signal. The ADC output value is heldin an adc_data signal and completion of the process is indicated by theanalog-to-digital converter logic on an adc_complete signal. Alsoillustrated in FIG. 7 is the pd_gain signal which is utilized to set thegain of the amplifiers before the ADC. This signal is shown as being setbefore the warm-up time to allow the analog circuit bias and signallevels to stabilize prior to conversion.

FIG. 8 illustrates a digital system controller 800 comprising a digitalblink detection subsystem dig_blink 802. The digital blink detectionsubsystem dig_blink 802 may be controlled by a master state machinedig_master 804 and may be adapted to receive clock signals from a clockgenerator clkgen 806 external to the digital system controller 800. Thedigital blink detection subsystem dig_blink 802 may be adapted toprovide control signals to and receive signals from a photodetectionsubsystem as described above. The digital blink detection subsystemdig_blink 802 may comprise digital conditioning logic and digitaldetection logic as described above, in addition to a state machine tocontrol the sequence of operations in a blink detection algorithm. Thedigital blink detection subsystem dig_blink 802 may be adapted toreceive an enable signal from the master state machine 804 and toprovide a completion or done indication and a blink detection indicationback to the master state machine 804.

FIGS. 9A through 9G provide waveforms, to illustrate the operation ofthe threshold generation circuit and automatic gain control (FIG. 5).FIG. 9A illustrates an example of photocurrent versus time as might beprovided by a photodiode in response to varying light levels. In thefirst portion of the plot, the light level and resulting photocurrentare relatively low compared to in the second portion of the plot. Inboth the first and second portions of the plot a double blink is seen toreduce the light and photocurrent. Note that the attenuation of light bythe eyelid may not be one hundred (100) percent, but a lower valuedepending on the transmission properties of the eyelid for thewavelengths of light incident on the eye. FIG. 9B illustrates theadc_data_held value that is captured in response to the photocurrentwaveform of FIG. 9A. For simplicity, the adc_data_held value isillustrated as a continuous analog signal rather than a series ofdiscrete digital samples. It will be appreciated that the digital samplevalues will correspond to the level illustrated in FIG. 9B at thecorresponding sample times. The dashed lines at the top and bottom ofthe plot indicate the maximum and minimum values of the adc_data andadc_data_held signals. The range of values between the minimum andmaximum is also known as the dynamic range of the adc_data signal. Asdiscussed below, the photodection signal path gain is different (lower)in the second portion of the plot. In general the adc_data_held value isdirectly proportional to the photocurrent, and the gain changes onlyaffect the ration or the constant of proportionality. FIG. 9Cillustrates the pd_pk, pd_vl and pd_th_mid values calculated in responseto the adc_data_held value by the threshold generation circuit. FIG. 9Dillustrates the pd_pk, pd_vl and pd_th_pk values calculated in responseto the adc_data_held value in some exemplary embodiments of thethreshold generation circuit. Note that the pd_th_pk value is alwayssome proportion of the pd_pk value. FIG. 9E illustrates theadc_data_held value with the pd_th_mid and pd_th_pk values. Note thatduring long periods of time where the adc_data_held value is relativelyconstant the pd_th_mid value becomes equal to the adc_data_held value asthe pd_vl value decays to the same level. The pd_th_pk value alwaysremains some amount below the adc_data_held value. Also illustrated inFIG. 9E is the selection of pd_th where the pd_th value is selected tobe the lower of pd_th_pk and pd_th_mid. In this way the threshold isalways set some distance away from the pd_pk value, avoiding falsetransitions on pd_data due to noise on the photocurrent and adc_dataheld signals. FIG. 9F illustrates the pd_data value generated bycomparison of the adc_data_held value to the pd_th value. Note that thepd_data signal is a two-valued signal which is low when a blink isoccurring. FIG. 9G illustrates a value of tia_gain versus time for theseexample waveforms. The value of tia_gain is set lower when the pd_thstarts to exceed a high threshold shown as agc_pk_th in FIG. 9E. It willbe appreciated that similar behavior occurs for raising tia_gain whenpd_th starts to fall below a low threshold. Looking again at the secondportion of each of the FIGS. 9A through 9E the effect of the lowertia_gain is clear. In particular note that the adc_data_held value ismaintained near the middle of the dynamic range of the adc_data andadc_data_held signals. Further, it is important to note that the pd_pkand pd_vl values are updated in accordance with the gain change asdescribed above such that discontinuities are avoided in the peak andvalley detector states and values due solely to changes in thephotodetection signal path gain.

FIG. 10 illustrates exemplary light-blocking and light-passing featureson an integrated circuit die 1000. The integrated circuit die 1000comprises a light passing region 1002, a light blocking region 1004,bond pads 1006, passivation openings 1008, and light blocking layeropenings 1010. The light-passing region 1002 is located above thephotosensors (not illustrated), for example an array of photodiodesimplemented in the semiconductor process. In a preferred exemplaryembodiment, the light-passing region 1002 permits as much light aspossible to reach the photosensors thereby maximizing sensitivity. Thismay be done through removing polysilicon, metal, oxide, nitride,polyimide, and other layers above the photoreceptors, as permitted inthe semiconductor process utilized for fabrication or in postprocessing. The light-passing area 1002 may also receive other specialprocessing to optimize light detection, for example an anti-reflectivecoating, filter, and/or diffuser. The light-blocking region 1004 maycover other circuitry on the die which does not require light exposure.The performance of the other circuitry may be degraded by photocurrents,for example shifting bias voltages and oscillator frequencies in theultra-low current circuits required for incorporation into contactlenses, as mentioned previously. The light-blocking region 1004 ispreferentially formed with a thin, opaque, reflective material, forexample aluminum or copper already use in semiconductor wafer processingand post-processing. If implemented with metal, the material forming thelight-blocking region 1004 must be insulated from the circuitsunderneath and the bond pads 1006 to prevent short-circuit conditions.Such insulation may be provided by the passivation already present onthe die as part of normal wafer passivation, e.g. oxide, nitride, and/orpolyimide, or with other dielectric added during post-processing.Masking permits light blocking layer openings 1010 so that conductivelight-blocking metal does not overlap bond pads on the die. Thelight-blocking region 1004 is covered with additional dielectric orpassivation to protect the die and avoid short-circuits during dieattachment. This final passivation has passivation openings 1008 topermit connection to the bond pads 1006.

FIG. 11 illustrates an exemplary contact lens with an electronic insertcomprising a blink detection system in accordance with the presentembodiments (invention). The contact lens 1100 comprises a soft plasticportion 1102 which comprises an electronic insert 1104. This insert 1104includes a lens 1106 which is activated by the electronics, for examplefocusing near or far depending on activation. Integrated circuit 1108mounts onto the insert 1104 and connects to batteries 1110, lens 1106,and other components as necessary for the system. The integrated circuit1108 includes a photosensor 1112 and associated photodetector signalpath circuits. The photosensor 1112 faces outward through the lensinsert and away from the eye, and is thus able to receive ambient light.The photosensor 1112 may be implemented on the integrated circuit 1108(as shown) for example as a single photodiode or array of photodiodes.The photosensor 1112 may also be implemented as a separate devicemounted on the insert 1104 and connected with wiring traces 1114. Whenthe eyelid closes, the lens insert 1104 including photodetector 1112 iscovered, thereby reducing the light level incident on the photodetector1112. The photodetector 1112 is able to measure the ambient light todetermine if the user is blinking or not.

Additional embodiments of the blink detection algorithm may allow formore variation in the duration and spacing of the blink sequence, forexample by timing the start of a second blink based on the measuredending time of a first blink rather than by using a fixed template or bywidening the mask “don't care” intervals (0 values).

It will be appreciated that the blink detection algorithm may beimplemented in digital logic or in software running on amicrocontroller. The algorithm logic or microcontroller may beimplemented in a single application-specific integrated circuit, ASIC,with photodetection signal path circuitry and a system controller, or itmay be partitioned across more than one integrated circuit.

It is important to note that the blink detection system of the presentinvention has broader uses than for vision diagnostics, visioncorrection and vision enhancement. These broader uses include utilizingblink detection to control a wide variety of functionality forindividuals with physical disabilities. The blink detection may be setup on-eye or off-eye.

In complex systems, which may include multiple sensors, such as poweredophthalmic lenses comprising a number of electronic components, it ispreferable to reduce the potential for initiating false actions or falsepositive triggering when taking action. In accordance with anotherexemplary embodiment, the present invention is directed to a decisionmaking process and/or voting scheme which utilizes input from multiplesensors to substantially reduce the possibility of changing the state ofthe powered ophthalmic lens based upon inaccurate, incomplete orerroneous information, changing physiologic conditions, as well as noiseand/or interference from internal and external sources. For example, inblink detection, the control system should not change the state of avariable-power optic incorporated into the powered ophthalmic lens basedupon a random blinking pattern due to eye irritation or the like. In apowered ophthalmic lens comprising a pupil convergence sensor, pupilconvergence may be utilized to trigger actions, for example, changingthe power of a variable-power optic to allow an individual withpresbyopia to focus on near distance objects. However, with input from asingle sensor or erroneous information from the single sensor or othersensors, incorrect decisions may be made by the system controller. Forexample, without knowing the position of both pupils, simply gazing downto the left may be detected as convergence by the right eye since thepupil has similar movement for both actions. In a powered ophthalmiclens comprising a lid position sensor, eyelid movement may also beutilized as a trigger for taking certain actions. For example, when anindividual gazes down to focus on a near distance object, the eyelidstend to droop and thus it may be utilized to change the state of theophthalmic lens. Once again, if only a single input is utilized, a falseaction may take place due to the fact that the person is sleepy andtheir eyelids droop. The same reasoning applies to sensors for detectingthe presence and locations of objects; namely, emitter-detector pairs,and pupil dilation sensors. All of these sensors may be utilized astriggers for action to be implemented by various systems incorporatedinto an electronic or powered ophthalmic lens, and all of themindependently or in limited combination are potentially subject toerror. In addition to the sensors already mentioned which are intendedto detect certain aspects directly related to triggering a state changein an electronic ophthalmic device, other sensors may be used to improvestate-change sensors by monitoring ambient conditions, noise, andinterference. For example, ambient light may be monitored to improve theaccuracy of blink detection, lid position, and pupil diameter sensors.Such sensors may be utilized to augment other sensors, for example, bysubtracting common mode noise and interference. Sensor inputs may beused to record a history readings which are then considered by a complexdecision algorithm, for example, one which considers both accelerometerinputs and eye muscle contraction to determine pupil position. Utilizingthe voting scheme in accordance with the present invention may reducethe likelihood of error in determining state changes and may also allowmore precise measurements. In other words, for any given action to betaken, there are sensors that may be utilized to check corroboratingevidence or to augment input for a given action determined by a primarysensor. It is also important to note that the sensed data, in additionto or in alternate use, may simply be utilized as part of a collectionprocess rather than as a triggering event. For example, the sensed datamay be collected, logged and utilized in treating medical conditions. Inother words, it should also be appreciated that a device utilizing sucha sensor may not change state in a manner visible to the user; ratherthe device may simply log data. For example, such a sensor could be usedto determine if a user has the proper iris response throughout a day orif a problematic medical condition exists.

Referring now to FIG. 12, there is illustrated an exemplary genericsystem in which sensors 1202, 1204, 1206 and 1208 are used to determineif the state of an actuator 1212 should be changed. The sensors 1202,1204, 1206 and 1208 may comprise any number of potential inputsincluding blink action, lid position, pupil position, ciliary muscleaction, and the like. The number and type of sensors is determined bythe application and user. Each sensor 1202, 1204, 1206 and 1208 may haveits own signal conditioning contained within the sensor block, adedicated block, or within the system controller 1210. The systemcontroller 1210 accepts inputs from each sensor 1202, 1204, 1206 and1208. It then performs routines to process and compare the input data.Based on these inputs, the system controller 1210 determines if thestate of the actuator 1212 should change. For example, the combinationof pupil convergence, lid droop, and an indication from anemitter/detector pair of a close reflection may trigger the systemcontroller 1210 to configure the actuator 1212 to change avariable-power optic in an ophthalmic lens to be in a near distancefocus state. Likewise, the combination of pupil divergence, lid opening,and indication from an emitter-detector pair of no reflections maytrigger the system controller 1210 to configure the actuator 1212 tochange the variable-power optic in an ophthalmic lens to be in a fardistance focus state. Inputs from various sensors may also be utilizedto alter the configuration of the system controller to improve decisionmaking performance, for example, if ambient light decreases, thecontroller may increase the gain of a photosensor. The system controllermay also turn sensors on and/or off, increase and/or decrease samplingrates, and make other changes to the system to optimize performance.

FIG. 13 illustrates an exemplary procedure by which a system controller,for example, system controller 1210 illustrated in FIG. 12, operates tosample sensors and change actuator status and ultimately the state ofthe powered ophthalmic lens. The first step in the process, representedby block 1302, is to sample the sensors. This may require triggeringother elements to activate, warm-up, calibrate, take readings,condition, and output data. The system controller may also provideconfiguration information to each sensor based on programmed values andcurrent data, for example, the gain of a photosensor amplifier based onthe history of incident light, or these settings may be determined byother elements in the system. The next step in the process, representedby block 1304, involves filtering and additional conditioning, forexample digital as opposed to analog filtering, along with a comparisonto baseline or reference results. The purpose of this step is toproperly condition the input data for the next step so that an accurate,repeatable decision may be made. The next step in the process,represented by block 1306, comprises determining the results from eachsensor, for example, the lid position and emitter-detector response.This determination may involve comparison to a pre-programmed orvariable threshold, comparison to a specific pattern, or any otherdetermination. The next step in the process, represented by block 1308,includes aggregating the results from the previous step, weighting theresults and making a decision. This step may involve per-user trainingand preferences, ensuring all sensors have been sampled before deciding,and various weights applied to the results of each sensor. Preferably,this step makes a decision that is predictable and repeatable in thepresence of real-world noise and interference. If a decision is made tochange the actuator status as described above, the next step in theprocess, represented by block 1310, comprises performing this statechange at the actuator. Regardless of the decision regarding statechange, the final step in the process, represented by block 1312,comprises returning the system to sampling so another set ofmeasurements and determination may take place. The total time requiredto execute the process in FIG. 13 is preferably short enough such thatthe system is responsive to user inputs similar to how individualsnaturally interact with their environments. For example, if utilized toactivate a variable-power focus lens, the system should change focusstate within approximately one (1) second, similar to that of thenatural accommodation system.

FIG. 14 illustrates multiple sensor inputs on the Y-axis plotted versustime on the X-axis. It is important to note that any sensor data may beutilized, depending on the application. For example, there are generallya minimum number of factors that may be utilized to independently verifyanother factor. In this exemplary embodiment, the system is designed todetermine the desired focal length for an ophthalmic lens as shown inplot 1400. The desired focal length oscillates from far 1402 to near1404, for example, from a user switching between distance vision tonavigate through a crowd and up-close reading of a map.

The additional plots shown above the desired focal length 1400 are thosefor various sensor inputs correlated to the desired focal length. Onceagain, it is important to note that any number of sensor inputs may beutilized to make a decision. Plot 1406 shows the impedance measuredacross the eye which varies from high impendence 1408 to low impedance1410, as is known in the relevant art. As illustrated, the plot ofimpedance 1406 does not precisely match that of the desired focal lengthplot 1400. The sensor input may include noise, delay, and otherdifferences from the desired focal length due to such phenomena asreaction time, propagation delay, and noise from nearby muscles. Pupilconvergence 1412 is also plotted versus time. As is known in the art,convergence of the pupils is associated with the attempt to focus on anearby object. When the desired focal length is far 1402, convergence islow 1414 because the pupils are close together relative to the distanceto the object under observation. When the focal length is near 1404, theconvergence is high 1416 because the object is close to the eyes whichmust turn their gazes inward toward the nose to keep attention on theobject of interest. Pupil diameter 1418 is also plotted. As is known inthe art, an individual's pupils typically dilate when focusing on anearby object. Accordingly, the dilation is shown as low 1420 when thedesired focal distance is far 1402. Dilation is shown high 1422 when thedesired focal distance is 1404.

It should be appreciated that each sensor input may vary for reasonsother than changes in the desired focal length. For example, the eyeimpedance may vary over time due to changes in body hydration, saltintake, level of exertion, or other means. Likewise, pupil diameter mayvary due to changes in ambient light levels. Thus, it should be apparentthat combining multiple sensor inputs reduces the chances of falsepositive triggering by requiring more than one input to correlate with adesired change in focal length or by using certain sensor inputs toaugment other sensors.

It should also be apparent that the thresholds for each sensor and thecombination of sensors used to determine a change in state depends onmany variables such as safety, response time, and user preferences. Thespecific programming of the voting scheme may be based on clinicalobservations of a number of subjects and individual programming tailoredto a specific user. Parameters in the voting scheme may be dependent onsensor inputs, for example, the threshold and gain setting for blinkdetection may vary with ambient light.

In one exemplary embodiment, the electronics and electronicinterconnections are made in the peripheral zone of a contact lensrather than in the optic zone. In accordance with an alternate exemplaryembodiment, it is important to note that the positioning of theelectronics need not be limited to the peripheral zone of the contactlens. All of the electronic components described herein may befabricated utilizing thin-film technology and/or transparent materials.If these technologies are utilized, the electronic components may beplaced in any suitable location as long as they are compatible with theoptics.

An intraocular lens or IOL is a lens that is implanted in the eye andreplaces the crystalline lens. It may be utilized for individuals withcataracts or simply to treat various refractive errors. An IOL typicallycomprises a small plastic lens with plastic side struts called hapticsto hold the lens in position within the capsular bag in the eye. Any ofthe electronics and/or components described herein may be incorporatedinto IOLs in a manner similar to that of contact lenses.

Although shown and described in what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope of the appended claims.

1. A method for controlling functions in a powered ophthalmic lens, themethod comprising the steps of: sampling multiple sensors incorporatedinto the ophthalmic lens, the sensors measuring at least one ofphysiologic or environmental changes; determining the results from themultiple sensors, including making comparisons to thresholds andcomparisons to predetermined patterns; aggregating the results from themultiple sensors to generate a single decision signal; and configuringan actuator based on the single decision signal to implement a change infunction of or maintain a function of the powered ophthalmic lens. 2.The method for controlling functions in a powered ophthalmic lensaccording to claim 1, wherein the step of aggregating the resultsfurther comprises weighting the inputs based upon a predetermined set ofconditions.
 3. The method for controlling functions in a poweredophthalmic lens according to claim 1, further comprising the step ofsignal conditioning the sampled output data from the multiple sensors.4. The method for controlling functions in a powered ophthalmic lensaccording to claim 3, wherein the step of signal conditioning includesone or more of filtering and comparing the sampled signals to baselineresults or reference results.
 5. The method for controlling functions ina powered ophthalmic lens according to claim 1, wherein the step ofsampling multiple sensors includes sampling sensors configured to sampleat least one of external conditions and physiologic changes not directlyrelated to the function to control to augment the generation of thedecision signal.
 6. A powered ophthalmic lens, the powered ophthalmiclens comprising: a contact lens including an optic zone and a peripheralzone; and at least on electronic system incorporated into the peripheralzone of the contact lens, the electronic system including multiplesensors, a system controller and at least one actuator, the systemcontroller configured to implement a process for controlling thefunctions of the powered ophthalmic lens, the process comprising thesteps of sampling the multiple sensors, determining the results from themultiple sensors including making comparisons to thresholds andcomparisons to predetermined patterns, aggregating the results from themultiple sensors to generate a single decision signal and configuringthe actuator based upon the single decision signal to implement a changein function of or maintain a function of the powered ophthalmic lens. 7.A powered ophthalmic lens, the powered ophthalmic lens comprising: acontact lens; and at least on electronic system incorporated into thecontact lens, the electronic system including multiple sensors, a systemcontroller and at least one actuator, the system controller configuredto implement a process for controlling the functions of the poweredophthalmic lens, the process comprising the steps of sampling themultiple sensors, determining the results from the multiple sensorsincluding making comparisons to thresholds and comparisons topredetermined patterns, aggregating the results from the multiplesensors to generate a single decision signal and configuring theactuator based upon the single decision signal to implement a change infunction of or maintain a function of the powered ophthalmic lens.
 8. Apowered ophthalmic lens, the powered ophthalmic lens comprising: anintraocular contact lens; and at least on electronic system incorporatedinto the intraocular lens, the electronic system including multiplesensors, a system controller and at least one actuator, the systemcontroller configured to implement a process for controlling thefunctions of the powered ophthalmic lens, the process comprising thesteps of sampling the multiple sensors, determining the results from themultiple sensors including making comparisons to thresholds andcomparisons to predetermined patterns, aggregating the results from themultiple sensors to generate a single decision signal and configuringthe actuator based upon the single decision signal to implement a changein function of or maintain a function of the powered ophthalmic lens.